Scanner/printer systems, such as a digital platemaker, a digital printer, a digital duplicate machine or a facsimile machine, which reproduce copies of an original document contain one or more photosensitive elements, such as a multiple photosite array of charge coupled devices, commonly referred to as CCD's, for scanning the original document to derive image data which is then made available to the image processing system for laser printing. When an original document in text form is scanned through a CCD, some of the information, such as in character strokes, may be lost, which can cause the characters to appear jagged, like stairs, after printing.
Heretofore, methods and apparatus for enhancing the sharp edges and details from an original imaging source have been known. Xue, Winans, and Walowit, "An Edge-Restricted Spatial Interpolation Algorithm," Journal Of Electronic Imaging, Vol. 1(2) at 152-61 (April 1992) address how to generate high spatial resolution image data from a low spatial resolution imaging source. They disclose an edge-restricted spatial interpolation algorithm developed to increase the image resolution and at the same time to enhance the sharp edges and details from the original imaging source. One of the disadvantages of using the algorithm disclosed by Xue, Winans and Walowit is that it scans the image in gray scale form, such that each input pixel has up to 256 variables. As a result, this system uses a costly and time consuming software program particularly in view of the time it takes to execute memory and input/output functions.
Chang and Tang, "New Transformation Of Control Points In Scaling Discrete Polygons," Journal Of Electronic Imaging, Vol. 1(2) at 162-70 (April 1992) disclose a bit mapping technique in a scanner/printer system for smoothing the edges of characters that are printed at a resolution that is higher than the resolution at which the characters are scanned. Bit map form uses two variable pixels, contrary to the gray scale form which uses a much more complex series of pixels having up to 256 variables. The bit mapping technique disclosed by Chang and Tang, however, uses an algorithm with pixels in a polygon data matrix form which again results in a system which uses a costly and time consuming software program.
Other image processing systems also teach enhancing the sharp edges and details from an original imagining source. However, these systems use hardware, not software, to accomplish such results. For example, U.S. Pat. No. 5,237,260, issued to Shimomae et al., discloses an image processing system for smoothing edges of an image. Unlike the methods and apparatus disclosed by Xue et al. and Change et al. which use software programs to smooth the edges of an image, the '260 patent discloses the use of optical and laser hardware to change the output pixel size in order to smooth the edges of an image. Similarly, U.S. Pat. No. 5,327,262, issued to Williams, discloses a system for detecting different types of image data and smoothing the contrast between such data. Williams uses standard integrated circuit component hardware to accomplish this result. The use of hardware, as disclosed in Shimomae et al. and Williams, increases the expense of the system compared to systems which use software.